Contact assembly for plug-in devices



May 2, W5 P. N. MARTIN 2,505,979

CONTACT ASSEMBLY FOR PLUG-IN DEVICES Fil d April 24, 1947 2 Sheets-Sheet 1 1w 9 Z6 Z 41b 16% 0 7 a 56% Z3 Q 5 6? I 6a 0 z I? 2 l j 250 Id IN V EN TQR. L P6612.

ATTORNEY May 2, 1950 P. N. MARTIN CONTACT ASSEMBLY FOR PLUG-IN DEVICES 2 STEBEtS-Sht 2 Filed April 24, 1947 1723a (action;

' INVENTORI l M 661 mm.

H21? ATTORNEY latentecl May 2, 1950 O A A SEMBLY FOR PL G- NDEY CE of Pennsylvania Application April-24, 1947;'Serial-N0.::743,605:

21 Claims. (01. 200 51.07)

My invention relates toa'contact assembly fori plug-in devices...

Contact assemblies. embodying my 7 invention are particularly'suitable for, although in. no way limited to, use in plug in relays for railwaysignaling systems, one form of which. relays is de: scribed in Letters Patent of the United. States No; 2,198,704., granted to Branko Lazich on. April 30,- 1940. One objectof my invention is to provide a contact assembly for such relays which assem bly can-be. constructed at a minimum cost and with the leastpossible expenditure of timeand effort.

Another ohj ect of my; inventionisto provide a contact assemblyionplug-in i devices, which. assembly can be readily inspected and cleanedin the assembled state and whichcanbe completely dismantled into its constituent parts, thus allowingior ease and lower cost in renewal or replace-. ment of suchpartsa Still another object of my invention is to pro vide acontact assembly for plug-in devices where-.. in means are provided for openingindividual cir. cuits for testin g -purposes without disconnecting the relayor disturbing any of the other circuits through the device According to. my invention, the .malev contact fingers-Of theplu ein deviceoare secured tc the. back plate. of the devicecby.mearisotweclgi g members in lieu. of the heretofore employed means whereby the contact. fingers, are permanently secured to .the hackplate or to apart thereof such as by the use of insulating blocks moulded around thefingers.

According to. my invention alsothe female connectorsof the plug-in device are detachably dis; posed in recesses in a plug receptacle in such manner that the contact surfaces are, readily ac: cessihle for inspection and cleaning inthe assem-L bled state, and in such manner that each" female connector can be individually dls'engagedfrom its associated male contact finger without disturbing: any of the othercontjactsthrough the device.

Other objects and characteristic features of my invention will appear as the description proceedsi I shall describe one form of contact assembly embodying-my invention, together with some al ternate methods wedging the male contact fingers in place; and shall then point-outthc novel features thereof rename.

In the accompanying drawings, Fi Lissa Ver tical sectional view showin portionsof the back. and mounting plates iforiazrelaygwhich back and. mounting plates are provided with contactgasseme. bliss embodyingamy invention. z-yis'an e1eya-.. tionalview of cthe... mounting plate. 2:: shown. in

2. Fig. 1342.3 lt eppears when viewed from, the left inFig, 1:

Fig. 3 is aJ-detail viewaxof one of the male contacti fingersshownin- Fig. 1. Fig. 4,is1-adetailview of: one of; the female connectors employed. in the mounting" plate; shown: in; Ei spl and .2. Fig. 5 is a. detail view-of one oi the clampin members. 5- showniin Fig: 1 as it appears when. viewedfrom the right in Fig. 1.; Fig..6 is a detail view of one r e larac ea emb rs fiv hownr n F 1 a i appears when viewed from theright in Fig. 1. Figs 7 is adeta viewrof one of the wedge mem hers '1' shown- Fig.- 1 ;as ;it1 appears :whenviewed from the-right in Fig 1. Fig; 8 ise. detail sectional view of a ,pQrtiongof the relaysbacloplate shown in -Fig.- l illustrating an alternate form for; the wedge memlcer shown; in Fig. 7 and further, illustrating bolt with a specially-formed head for usewitltsucl nalternate form. of wedg e member. Fig.9 isasecti naI-viewof aportiontofpthe relay-back plate; shown. in; Fig. 1 illustrating another; form of clamping arrangement also emsbodying my invention whereby am ore positive weaging oi the contactfingers in place, is produced. Fig. IOwis a-seotional view of a portionv oftharelayback plate shownin Fig. 1 illustrating: still another; form :of clamping arrangement for securingthqamale contact fingers in; place and;

also embodyingmytinvention. Fig. 1 1. is an isometric View ot the relayback plate shown in} Fig. 1. Fig; IZAsa fr-agmentarysectional view of a? medifiec orni; 0f he: el ack l te n s clamping, members shown in Fig. 1 embodying. my v n ion-i Similar reference; characters refer to similar parts each of; the several viewsj l qt fi r wi gs aY hq l a contact assembly embodying my invention-in the. form it. assumes: when... usedin connection with a; plug-in; relay and; associated mounting;

pl t fr hew rpe o n ari- 3 1 Patten? 2,198,704, referregl to hereinbefore but it should be: understood; ;at,;the outset that: my; inventions n mitedlt h sv a t q la r asm has the plusv n-m ar n unt ap a re n w scribedin detail in th said Patent No. 2,198,704; only those parts of; the relay and. mounting plate which areenecessary; ior a: clear. undertanding.

of mypreSfiIitdnvention have. been shown and will be. described zherei n. The portions of l the relevand:mountingplate which are shown co:m-, prise.thenlowenhalt oig theibackiplate I ofthe.

Thezsectiongof theimounting plate 25 shown iii-Fig. 1 is taken substantially on the line; ---I of Fig. 2; and the section of the back plate I shown inFigg l istaken onya,correspondingplane.

ti relay and the corresponding lower half of the mounting plate 2.

Formed on the front face of the back plate l which is of insulating material is a raised portion la provided with openings lb (see Fi 11) for receiving a plurality of contact fingers 3 (see Fig. 1) disposed in grooves lc (see Fig. 11) moulded in the back late at the tops and bottoms of the openings. Each opening communicates with a rectangular cavity ld (see Fig. 11) formed in the rear face of the back plate. The rear ends 3a of the contact fingers extend into cavity id and constitute plugs for making connection with suitable female connectors 5 mounted in the mounting plate 2'. All of the contact fingers disposed in the grooves of any one opening are secured in the back plate by means of a rear clamping member 5, a front clamping member and a wedge member 7 in combination with bolts 8. The bolts pass through clearance holes la, ta and 5a in the wedge member, front clamping member and rear clamping member, respectively, and are screwed into threaded inserts 5b moulded in the rear clamping member. Each clamping member 5 is of insulating material, and is of such dimensions that a snug fit is obtained with all four sides, excluding recessed portions formed by grooves lc, of the associated opening lb. Each clamping member 5 is provided with rectangular-shaped lug projections 50 which extend into correspondingly shaped holes 3b in the associated contact fingers 3 and serve to lock the contact fingers in the grooves lc in the proper front-to-rear alignment as viewed in Fig. 1. Each front clamping member a is of channel-shaped insulating material and is dimensioned with respect to the sides of opening lb similar to the rear clamping member. Each wedge l is of metal and is so shaped that when wedged into the channel-shaped front clamping member it from the open side a spreading apart of the two opposite sides of the member 6 is produced. The maximum width of the wedge is such that a light force fit will be had when it is forced against the inner extremity of the channel member.

An alternate design of wedge member which can be used with the channel-shaped member 6 in place of the wedge member 'l is shown in Fig. 8. Referring to Fig. 3, it will be seen that the wedge member which is here designated by the reference character 9 consists of a thin piece of spring metal curved in cross section for use with a bolt in having a specially shaped head to conform to the concave surface formed by the spring metal piece 9 when piece 9 is wedged into channel-shaped member 5. here that wedge members 7 and 9 may not necessarily consist of one piece for a single opening lb but may consist of separate wedges for one or more sets of upper and lower contact fingers 3. The parts referred to hereinbefore are assembled in order to obtain the desired clamping action as follows. First, the contact fingers 3 for each opening lb are pushed through the opening into the back plate cavity id to such positions that the rear clamping member 5 can be inserted between the projecting portions of the respective upper and lower rows of contact fingers 3, the top and bottom lugs 5c of the rear clamping member being disposed in the holes 313 in the contact fingers. With the contact fingers properly aligned with respect to each other and to the rear clamping member, the fingers together with the clamping member are drawn It is to be noted back into opening lb until the front face of clamping member 5 is in firm contact with shoulders le which are formed in the opening integrally with the back plate as shown in Fig. ll. Next, the bolts 8 are passed through clearance holes la and 6a in the associated wedge member and front clamping member 6, respectively, and this assembly is inserted into opening lb between the frontal projecting ends of the upper and lower rows of contact fingers to a depth necessary to allow the threaded bolt ends to extend through clearance holes 5a and engage moulded inserts 5b in the rear clamping member 5. Finally, the bolts 8 are screwed into the moulded inserts until the rear face of the front clamping member 6 is in firm contact with shoulders lo, the wedging and clamping action of the contact fingers being complete at this point.

Another method of securing the contact fingers 3 in place is shown in Fig. 9. Here, a rear clamping member ll is provided of similar design to the front clamping member 6 except that top and bottom lugs lid, similar to lugs 5c, are provided on clamping member ll for engaging holes 3b in the contact fingers. Likewise, there is associated with the clamping member ll a wedge member l2 similar to the wedge member 5 associated with the front clamping member except that tapped holes l2a for engaging clamping bolts l3 are provided in wedge member :2. With this construction of parts both front and rear clamping members, when drawn by the bolt l3 into opening lb between the upper and lower rows of the contact fingers in any one opening, act to wedge as well as clamp the fingers in the grooves lc.'

Fig. 10 is illustrative of still another method of securing the contact fingers 3 in place. In this method a rear clamping member M is employed of substantially the same design as rear clamping member 5 of Figs. 1 and 5 including associated lugs Ma for engaging holes 3b in the contact fingers. Clamping member l4 differs from clamping member 5, in one respect, however, in that member lfil is of such width that its rear part projects into cavity ld between the contact finger end portions 3a. This projecting part may extend for any length up to but not beyond the projecting contact finger end or plug portions by reason of the novel construct on of the mounting plate 2 and associated female spring connectors 4. Such novel construction provides for one only female connector to contact one side only of each contact finger plug portion (1. e., the top and bottom sides of all top and bottom contact fingers, respectively, disposed in an opening lb), and will be described more fully later in this specification. The purpose of extending the rear part of clamping member I4 is to reinforce by backing up the non-contact sides of the contact finger plug portions and it is to be understood that similar members could be employed in the assemblies of Figs. 1 and 9 as substitutes for rear clamping members 5. llhe front clamping member IS in the method of Fig. 10 is a rectangular block of insulating material of the same dimensions with respect to the sides of opening lb as the rear clamping member l4, and is provided with spaced bolt-head recesses l5a in the front face termimating in clearance holes l5b. Recesses l5a and clearance holes l5b are aligned with correspondingly spaced clearance holes Nb and moulded inserts ldc in rear clamping member l4. Each group of aligned recesses, clearance holes and roomers- 5i moulded inserts i has i disposed therein a bolt I B and both clamping members are secured'in the it opening lb in firm contact with opposite sides ofshoulders le when-the-bolts" lfi -arescrewed up tightly in the moulded inserts Me. A. locking of the contact fingers 3 in place is'efiected' by this action as a-result oi the engagement of lugs "Mo inthe rear clampingmember with -holes' 3b inthe contact fingers. A wedgi-ng of the cons tact fingers i 'is producedby inserting in each ofeither the top or bottom-grooves in an opening a specially shaped-spring l'lot flat spring ma terial between the groove andthe associated" contact finger. The. springs li are compressed when the front and rear clampin members are drawn into opening lb by'bolts l5 andsufii'cient stresssis' developed in the springs il to obtainathe: desired .wedging force. It is evident. that in this. method the grooves. ij having :thecsprings ll dis posedltherein arenecessarily of greater dimension:.inz.depth' than are. the remaining grooves I c by. anamount consisting of the overall thicknesstofx a spring ll when. compressedtoobtain the aforesaid. desired .wedging force.

The. view in Fig. 12.: is a slight modification of the means shown. intFigl'l for securing the contactfingers 3 in place. In this view rear fronticlamping members 2i and 22 .are of sub.- stantially the same. construction. as rear and. front clamping members; .5- and g. respectively, with. the exception that. grooves 25a and 22d. for::aligning the contact'fingers dare provided in'rthe rearand front clamping. members, 25 and 22;. respectively, and the grooves lc of Fig. 1 are..eliminated. Lugs 2th and moulded inserts Zlc are. accordingly of similar construction to lugs '50. and. moulded inserts 5b, respectively.

It. is obvious from the foregoing description. that the individual male contact fingers-are read ily detachable from the back plate for purposes of renewal or replacement. The advantages of such an. assembly over:one in which a plurality of. contact fingers are permanently moulded in" multiple within insulated: blocks.- which are in turn secured to the backiplataor one in which the contact.fingersareotherwise permanently secured to: the relay 'backxplate; such as by use of a swaging tool, are likewise obvious. Certain contact blockassernblies: have": as many-as eight contact fingers moulded there in per block and must .be handled very carefully to avoid damaging of contacts. The'described manner of assembling contacts obviates thisrlast. mentioned difficulty andalso eliminates theproduction complication oi. cleaning and plating contact fingers after they have been moulded in the. contact blocks. or otherwise. permanently secured to the relay back plate. The reduced. production costs broughtaboutby .thesaving in time required to assemble the contactsin the backplate as described over that required to mould the contacts in blocks or to otherwise: permanently secure them, constitutes another advantage of t -e described'method. Lastly, the comparative ease of moulding a back'platewith few relatively large openings rather than one. with many small slots is an advantageiof the described method of contact assembly. A further simplificationofthe base plate mould is obtained: byproviding the grooves for aligning th'econ tact fingers in the front and rear clamping meme ber-s instead of in the back plate.

The mounting plate 2 is of insulatingmaterial;

and is intended to be securedsin .a:.vertical ..position to: a it suitable. sup port in;such1.manneri thati 1' g. access to= the rear -"facerof 1 the mountiugo plate 5 may' be readily had: The construction of the support and the means for securing the mount-i ing plate to it form no part-"of my zpresent invention, and are therefore =not shown.

Formed on the fr'ontside of the mounting plate its a rectangular"projection 2a, whichlenters the. cavitydd in the. relay back plate 'I whenthe relay: isplugged into the-mounting plate; Theprojec tionZdis provided with' rectangular recesses 26,

eachone of which' receives theplug portions 3w of two rows ofhoriz'ontally aligned relay contact fingers. Recesses 2bcommunicate at their inner ends-with rectangular holes 20 disposed slightly:

.. above and belowth'eupper and lower sides of the recess, the end holes having their extreme in terior surfaces in alignment with the interior end surfaces of therecess. Each of the holes l is. spaced for'alignment-with one of the relay contact fingers; Each hole 2c is dimensioned 1 in width to receive one of the female connectors fl referred to hereinbefore; and communicates atits outer end with a shallow recess Zd formed in the rear face ofmountingplate 2 to receive-a retaining plate I3; Each hole-2o is provided with a'recess 2c in its side opposite-to-the side common to ei ther the upper orlowerside of-recess- 2?) do pending on whether the hole isdisposed adjacent" to theupper or thelower side: Recess-zc extends fromthe outer endof hole' 20 inwardly to a point intermediate the recess Zb and shallow recess 2d for a purpose to be explained" hereinafter. Re tainingplate i l 8 is of "insulating material secured bymeans of screws I9 to'the'm'ounting plate 2" and is provided with a pluralityof slots i812. throughwhichthe tail'portions lla of connectors 4 extend with considerableclearance; Disposed ineachhole 2.01s a middle portion of one female connector-d;- the front portion of which extends into the recess Eb and le -restrained as viewedin' Fig: 1 from movement to the left bylip 2 formed at the front edge oi -recess 2b; As previously; stated the rear ortail portions 412 of theconnectors extend through slots I811 in' the' retaining plate lawhich plate serves-to restrain theconnectors, from movement to the-right; as viewed in l, bymeansof shoulders 42) formed in the connectors. Each female connector 4 as here shown is constructed of a single piece of metal and isprovided at the'end oppositethe tail poritsmiddle and front portions against the afore said side of.:a hole 2c;common to either the upper or lower sidelof recess 21). The shorter leg of eachconnector tis urged at its free end, when the reiay ishotztplugged in, against the-aforesaid side of hole 2o oppositetotheisaid common side due to-its inherent resiliency, thereby holding the connector tlsecurely-in place within the mounting plate. The shortertleg of each connector 4 also constitutes a surface for making contact with one side of one contact finger plug portion 3a. Since all female connectorsd in any one recess Zbabut against either the top or the bottom side of the recess irr'alignmentwith two horizontal rows of contact fingers 3 and sincei'each connector a con-. tacts one side only'of a contaot'finger plug portion,zitcan-beseen that all plug portions of the upper row: of contact fingers are contacted on their top. sidesand all plug portions of the lower row of: contact-fingers are contactedzon their hottomzsidesi Such an arrangement of parts p=rovides withina recess 2b for anunobstructed space betweenrcontactzsurfacesrofupper and: lower fe male spring connectors equal to the vertical spacing of the two horizontal rows of contact fingers whose plug portions are received in such recess. The short leg of each connector 4 is split lengthwise by a slot 40 (see Fig. 4) in order to facilitate making a good electrical contact with the plug portion 3a of the associated contact finger 3 when the parts are in their normal plugged-in positions as shown in Fig. 1. It is intended that the outer end of each female connector 4 be permanently connected to an external circuit wire 20 (see Fig. 4), and to facilitate fastening the circuit wires to the outer ends of the connectors the tail portion 411 of each connector is pierced by a hole 4d (see Fig. 4) and is provided in its opposite edges with notches 4e.

A feature of the invention is embodied in the provision of the recesses 2c in the holes 2c and in the-provision of considerable vertical clearance of the tail portions 4a of connectors 4 in the slots Isa. This clearance is such that the shoulder 4!) of each connector 4 can be drawn rearwardly through the associated slot lBa when the tail portion 42) is urged away from the upper or lower, as the case may be, side of the slot so as to bring the shouldered portion of the connector into alignment with the slot. The outer edge lBb of this upper or lower side of the slot 18a is beveled for the purpose of inserting a wedging tool between the connector tail portion 4a and the adjacent side of the slot. The lower connector 4 shown in Fig. 1 in dotted outline is illustrative of the condition in which any of the connectors 4 is drawn rearwardly through the slot liia to an extreme position. In this position it will be noted thatthe free end of the short leg of connector 4 has been urged by its inherent resiliency into the corner formed by the recess 2e and the retaining plate 18 to prevent a complete withdrawal of the connector. Thus, one or more individual connectors 4 may be disengaged from their associated contact fingers 3 without disturbing any of the other engaged contacts in the device.

. The principal advantage of the form of mounting plate or receptacle and associated female connectors which I have described above resides in the facility with which the contact surfaces of the described connectors can be inspected and cleaned in the assembled state. Such ease of access to female contact surfaces is not provided in older forms of multiple contact plug-in devices wherein access of a mating contact finger to a pair of enclosed female connectors spaced so that their inherent resiliencies are opposed to each other is aiiorded through a narrow slot. The described open type of plug receptacle has another advantage in that the mating contact fingers do not have to be maintained in precise alignment with respect to the female plug receptacle as is necessary in devices in which access of a plurality of contact fingers to female spring connectors is had through a plurality of small slots.

Another important advantage of the abovedescribed mounting plate and associated female connectors is derived from the individual circuit opening feature wherein one or more female connectors may be withdrawn out of engagement with their associated male contact fingers without disturbing any of the other circuits through the device by unplugging the relay or removing the female connector securing means, and wherein the disengaged female connectors are prevented from being completely withdrawn from the mounting plate. Individual circuits may therefore be opened as desired for testing or any 8 other purpose. A distinct advantage resides in the prevention of complete withdrawal of the connectors since there is no possibility of connectors being interchanged and improperly reassembled when more than one are withdrawn at the same time.

Although I have herein shown and described only one form of contact assembly for plug-in devices embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In a plug-in device, a mounting plate of insulating material having a plurality of recesses formed in one side of the plate each of which communicates at its inner end with a plurality of holes disposed adjacent to two opposite sides of the said recess, which said holes, in turn, communicate with the other side of the plate, a cover member provided with a plurality of clearance slots and secured to said mounting plate adjacent the outer ends of said holes, and connectors one of which is disposed in each of said holes and each of which projects into a said recess for making contact with one side of the plug portion of an aligned contact member inserted into the recess, each said connector being formed with a tail portion extending through one of said clearance slots in said cover member, said tail portion providing means for attaching external circuit wires to the connectors, and each said connector being restrained from longitudinal movement within a said recess, a said hole and a said clearance slot by a lip formed integrally with the said mounting plate at the outer end of said recess and a shoulder formed in the connector at the junction of the said mounting plate with the said cover member.

2. In a plug-in device, an insulating mounting plate provided in one side with a plurality of recesses each of which said recesses communicates at its inner end with a plurality of holes disposed adjacent to two opposite sides of the recess, which said holes communicate with the other side of said mounting plate, connectors disposed one in each of said holes and projecting into said recesses for making contact each with one side of the plug portion of a different contact member in serted into the recess, said connectors extending out through the holes on the other side of said mounting plate, each said connector being formed with a shoulder to secure said connector within the associated recess and hole, the shoulder recess and hole being so proportioned that each connector may be individually disengaged from its associated contact member by manipulation of the extending portion of said connector.

3. In a plug-in device, a mounting plate of insulating material having a plurality of recesses formed in one side of the plate each of which communicates at its inner end with a plurality of holes disposed adjacent to two opposite sides of the said recess, which said holes, in turn, communicate with the other side of the plate, a cover member provided with a plurality of slots and secured to said mounting plate adjacent the outer ends of said holes, and connectors one of which is disposed in each of said holes and each of which projects into a said recess for making contact with one side of the plug portion of an aligned contact member inserted into the recess, each said connector being formed with an outer tail iap'ortionl extending "with rconsiderable ."clearance throughnan'cassociatedwone:oi said slots in said rccover. member andreachrsaid. connector being restrained from,iongitudinahmovement within the associated: recess, .hole; =1 ands-slot by a lip formed H integrally withsaid mounting plate at the outer .end of the recessanclwa shoulder formed in the connector at the junctionxof "said mounting plate with said cover member, the clearanceof each said slot being suchras -.to permit the passing of the shouldered portion ofthe associatedconnector when said shoulder is urged into alignment with the slotand the connectoruis withdrawn outwardly from its associated hole itosthe position inwhich its inner. endis outcoiengagement with its associated-contact memberzand in which fur .ther withdrawal is prevented by the engagement ofits .inner end with the said cover member.

4. In a-plus-in device-the combination-wither back plate of. insulating. material provided with a cavityin itswrear facevand' with a, plurality of openings communicating with said cavity, each .ofwhich said openings communicates in two opposite sideswi-th aplurality of grooves for the re- ..oeptionof two horizontal rows of contact fingers having plug portions projecting into said cavity, and whichsaid fingers cooperate with and are se- 1 cured one .in eachof said grooves tby clamping means providedinsaid openingaof an insulating mounting plate having a raised portion adapted" to fit into said cavityrand provided in said raised portion with recesses iorthe'reception in each of the. said plugportionst of the said two horizontal .rows of contact fingers, each of which said recesses communicates atits inner end witha plurality-of holes disposed'iadjacent to two opposite .sides of the recessin alignmentwith the said two horizontal rows of contact fingers, and each of which said holes communicateswith the rear face .of said mounting plate-and has secured therein oneconnectorwhich projects into said recess for making contact with one side of asaidcontact finger plug portionso that the contact surfaces of all such connectorsin any one ofsaid recesses .are readily accessible in the assernbled state and so that suitable .:reinforcement of the plug portions of said contact fingers in the unobstructed. -space within said recess-and between the noncontact surfacesof the said twohorizontalrows of .the fingers can be provided. for.

5. In a. plug-imdevice, an insulating mounting .-131Elt having. inutheufrontsidethereof at least one recess and an aperture of substantially smaller. crossesection than therecessand. extend- Ling between the .bottom of the recess .andthe back side of the plate, said plate being formed with a lip adjacent the front of said one interior surface of the recess,.a connector of yieldable material inserted in said aperture from the back side of the plate, said connector being offset with relai ly short leg substantially U-shaped and a ely long leg with its end projecting through the back of the plate, said .lip being effective tvhenltheconnector is in place to engage the c osed end of. 'iJ-shaped legand limit its "d movement, axcoverior the back ofisaid lg plate having an aperture therein for the "of the long leg of the connector, said closing said plate. aperture so as to form a shoulder aligned with said one surface of the plate-aperture, theoffset of theconnector io; mine a. shoulder: adapted to engage said cover shoulder hen the closed;end of the U-shaped short le aging the lip; said: shortlegoi the for" mount n of) :oonnector being clonger than. theLdenth of; the: re-

.cess;sovasvtoxyieldably engage: the surface of the aperture opposite-said; onesurface and thereby :hold the long leg :of the connector against said one surface. and the connectorshoulder against :5 the cover shoulderysaid' cover aperture being sufficiently*widerdthan'the connector to permit a lateral inoveinentthereof by'manipulation of the rearwardly projecting :end of the long leg so as :tO disengage the shoulder onsaid connector from thecoverplate and permit withdrawal of the long log through: SQidfCOVBI. aperture.

.6. 'plug in :device, an insulating mounting fiplat; having in theirront side thereof at least one recess (and tan aperture of substantially -sniallertcross'-section than the recess and extend- ?ing .between itheebottoniiof.the:recess and the back. side of :the :plate; said; aperture. having: one .interiorsurface: aligned with aninterior surface of the recess, said plate being formed withalip adjacent "the IZiL'OIltR. of said one interior surface of 'therrecess,.arconnector of yieldablexznaterial .sinserted' inzsa'idi aperture from'theback side of i the :piataJsaid connector. being offset with a relativelyirshortrby substantially .U- shaped. and a as relatively long legiwith its endprojecting through the back of .the plate, said lipfbeing efiective when'ithesconnector is in'zplaceto engage the closed end of the :Ut-Fshaped. short leg and limit its forward movement, 'a .cover for the back 'of 39', said iinounting? 'plate"havingi an aperture therein forthe passageiof .the long legof the connector,

- said coverxpar'tiall'y closingsaidplate aperture so as to form ashoulderialignedwith said one suriace of the: plateaperture; said. olisetof the conarnectcr forming .a. shoulder adapted to engage flsa'id ooverishoulderiwh'en the closed end-of the u-shapedshortieg is engaging'the lip, said short leg of. the connector-being longer than the depth of the recess so asto yieldably engage the surface of the aperture opposite said one surface and thereby 'hold the long leg of the connector against said one surface and the connector shoulder against the cover shoulder, said cover aperture being suiilciently'wider than the connector leg toperrnit a lateral -movement thereof by rnanipulation of its rearwardly projecting end so as to "disengage the shoulder on said connector from "the cover plate and permit withdrawal of the v connector leg through said cover aperture, said plate aperture and cover aperture being contoured'so as toform another shoulderaligned with the surface of theplate aperture opposite said onesurIaceysaid other shoulder being effective to engage .the' short. connector leg during withdrawal of therconnector through the cover aperture and thereby limit such withdrawal.

7.111 aplug-in device, a mountingplate, at least one connectorin said mounting plate for making contact withan associated contact. memberin .an...associated.coupling member, said con .nector having an and .projecting from said mounting plateand beingmovable between afirst position in which it engagesits associated contact member and a-second position in which it is disengaged therefrom, and means including a portionof the connector for holding the connector in its .first position, said holding means being completely releasable by;.rnanipulation of the sprojecting'endzof the connector'to move said con- "nectorinto its second position by partially withdrawingsaid connector from said-mounting plate. 8. In a plugein-i device. a mounting plate, at least onerconne'ctor in saidxmounting"plateifor '35 -malzingccontactrwithwan associated oontactunember in an associated coupling member, said connector having a contact portion movable between a first position in which it engages its associated contact member and a second position in which it is disengaged therefrom, said connector also having a latch portion movable between a latching position wherein it is effective to hold said contact portion in its first position and an unlatching position wherein it permits movement of the contact portion to its second position, and means including said mounting plate for supporting said connector with an end portion thereof projecting externally of the mounting plate and movable relative thereto in a direction to move said latch portion to its unlatching position and thereafter in a direction to move said contact portion to its second position by partially withdrawing said connector from said mounting plate.

9. In a plug-in device, an insulating mounting plate having in one side at least one recess and at least two apertures substantially smaller than said recess and extending between the bottom of the recess and the opposite side of the plate, said apertures being located on opposite sides of the recess, a pair of connectors, one in each aperture, said connectors extending into the recess along opposite sides thereof, a coupling plate member of insulating material having at least one opening extending therethrough, a pair of contact fingers, clamping means extending through said opening and contoured to form therewith a pair of apertures to receive said contact fingers, said fingers having ends extending beyond the coupling plate member so as to leave the outer faces of the finger ends open, the width of said clamping means being related to the width of said recess so that the fingers are insertable in the recess to bring their outer faces into contact with the connectors on opposite sides of the recess, each said connector having an end projecting from said mounting plate and being movable between a first position in which it engages its associated contact member and a second position in which it is disengaged therefrom, and means including a portion of the connector for holding the connector in its first position, said holding means being completely releasable by manipulation of the projecting end of the connectorto move said connector into its second position by partially withdrawing said connector from said mounting plate.

10. In a plug-in device, a plate member of insulating material having at least one opening extending therethrough, said plate member being formed with oppositely and outwardly facing shoulders within said opening, a contact finger, a pair of clamping members in said opening, each abutting one of said shoulders, said clamping members and plate member being contoured .to form between them aligned apertures to receive said contact finger, and means engaging both said clamping members to hold them against their respective shoulders.

11.,In a plug-in device, a plate member of insulating material having at least one opening extending therethrough, said plate member being formed with oppositely and outwardly facing shoulders within said opening, a contact finger, a pair of clamping members in said opening, each abutting one of said shoulders, said clamping members and plate member being contoured to form between them aligned apertures to receive said contact finger, one of said clamping members and said contact finger having surfaces con- 12 toured to mechanically interlock and hold said finger in place in said apertures, and means engaging both said clamping members to hold them against their respective shoulders.

12. In a plug-in device, a plate member of insulating material having at least one opening extending therethrough, said plate member being formed with oppositely and outwardly facing shoulders within said opening, a contact finger, a pair of clamping members in said opening, each abutting one of said shoulders, said clamping members and plate member being contoured to form between them aligned apertures to receive said contact finger, means engaging both said clamping members to hold them against their respective shoulders, and resilient wedging means associated with at least one of said clamping members to aid in holding said members and said finger in their proper relative positions.

13. In a plug-in device, a plate member of insulating material having at least one opening extending therethrough, said plate member being formed with oppositely and outwardly facing shoulders within said opening, a pair of contact fingers, a pair of clamping members in said open ing, each abutting one of said shoulders, said clamping members and plate member being contoured to form between them opposed pairs of aligned apertures to receive said contact fingers, one of said clamping members having a U-shaped cross-section with the sides of the U engaging said contact fingers, a wedge member movable between the sides of the U-shaped member to spread the sides and force them into engagement with the contact fingers, and means eifective simultaneously to force the wedge member to spread its associated clamping member and to hold both clamping members against their respective shoulders.

14. In a plug-in device, a plate member of insulating material having at least one opening extending therethrough, said plate member being formed with oppositely and outwardly facing shoulders within said opening, a pair of contact fingers, a pair of clamping members in said opening, each abutting one of said shoulders, said clamping members and plate member being contoured to form between them opposed pairs of aligned apertures to receive said contact fingers, means engaging both said clamping members to hold them against their respective shoulders, a laterally compressible spring extending through one of said pairs of aligned apertures, and means effective simultaneously to hold both clamping members against their respective shoulders and to compress said spring to hold the fingers in their assembled relation.

15. In a plug-in device, a plate member of insulating material having at least one opening extending therethrough, said plate member being formed with oppositely and outwardly facing shoulders within said opening, a pair of contact fingers, a pair of clamping members in said opening, each abutting one of said shoulders, said clamping members and plate member being contoured to form between them opposed pairs of aligned apertures to receive said contact fingers, and means engaging both said clamping members to hold them against their respective shoulders.

16. In a plug-in device, a plate member of insulating material having at least one opening extending therethrough, said plate member being formed with oppositely and outwardly facing shoulders within said opening, a pair of contact fingers, a pair of clamping members in said opening, each abutting one of said shoulders, said clamping members and plate member being contoured to form between them opposed pairs of aligned apertures to receive said contact fingers, said fingers having ends extending beyond said plate and said clamping members so as to leave the outer faces of the finger ends open, and means engaging both said clamping members to hold them against their respective shoulders.

17. In a plug-in device, an insulating mounting plate having in one side at least one recess and at least two apertures substantially smaller than the recess and extending between the bottom of the recess and the opposite side of the plate, said apertures being located on opposite sides of the recess and each having one interior surface aligned with one surface of the recess, and a pair of connectors, one inserted in each said aperture from said opposite side of the plate, said connectors extending into the recess along opposite sides thereof to make contact with opposite faces of spaced contact members inserted in the recess.

18. In a plug-in device, an insulating mounting plate having in one side at least one recess and at least two apertures substantially smaller than the recess and extending between the bottom of the recess and the opposite side of the plate, said apertures being located on opposite sides of the recess and each having one interior surface aligned with one surface of the recess, and a pair of connectors, one inserted in each said aperture from said opposite side of the plate, said connectors extending into the recess along opposite sides thereof to make contact with opposite faces of spaced contact members inserted in the recess, said recess being substantially wider than said connectors so as to provide ready access through said recess to the contacting surfaces of the connectors therein.

19. In a plug-in device, an insulating mounting plate having in the front side thereof at least one recess and an aperture of substantially smaller cross-section than the recess and extending between the bottom of the recess and the back side ment, a cover for the back of said mounting plate having an aperture therein for the passage of the long leg of the connector, said cover partially closing said plate aperture so as to form a shoulder aligned with said one surface of the plate aperture, said offset of the connector forming a shoulder adapted to engage said cover shoulder when the closed end of the U-shaped short leg is engaging the lip, said short leg of the connector being longer than the depth of the recess so as to yieldably engage the surface of the aperture opposite said one surface and thereby hold the long leg of the connector against said one surface and the connector shouider against the cover shoulder.

20. In a plug-device, an insulating mounting plate having in one side at least one recess and at least two apertures substantially smaller than said recess and extending between the bottom of the recess and the opposite side of the plate, said apertures being located on opposite sides of the recess and each having one interior surface aligned with one surface of the recess, a pair of connectors, one in each aperture, said connectors extending into the recess along opposite sides thereof, a coupling plate member of insulating material having at least one opening extending therethrough, a pair of contact fingers, clamping means extending through said opening and contoured to form therewith a pair of apertures to receive said contact fingers, said fingers having ends extending beyond the coupling plate member so as to leave the outer faces of the finger ends open, the width of said clamping means being related to the width of said recess so that the fingers are insertable in the recess to bring their outer faces into contact with the connectors on opposite sides of the recess.

21. In a plug-in device, an insulating mounting plate having in one side at least one recess and at least two apertures substantially smaller than said recess and extending between the bottom of the recess and the opposite side of the plate, said apertures being located on opposite sides of the recess and each having one interior surface aligned with one surface of the recess, a pair of connectors, one in each aperture, said connectors extending into the recess along opposite sides thereof, a coupling plate member of insulating material having at least one opening extending therethrough, a pair of contact fingers, clamping means extending through said opening and contoured to form therewith a pair of apertures to receive said contact fingers, said fingers and said clamping means having ends extending beyond the coupling plate member so as to leave the outer faces of the finger ends open, the width of said clamping means being related to the width of the recess so that the ends of the fingers and the clamping means are insertable into the recess to bring the outer faces of the fingers into contact with the connectors on opposite sides of the recess, the extending end of the clamping means being then effective to prevent distortion of the finger ends.

PAUL N. MARTIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,917,009 Betts et al July 4, 1933 2,124,182 Braun July 19, 1938 2,220,810 Bright Nov. 5, 1940 2,258,122 Merkel Oct. 7, 1941 2,391,324 Martin Dec. 18, 1945 2,397,283 Martin Mar. 26, 1946 2,457,703 Merkel Dec. 28, 1948 

